above ground storage tank (API 650) operating limits

[MAG1985]

Hi all.
We had incident of empty styrene tanks where the breather valves taken out and nozzles blinded, atmospheric temperature went down enough to cause a partial collapse of the tank.

Process engineering request us to specify the limitations of operation such as level, temperature and pressure.
API 650 in which this tanks was constructed, nothing specific.

I would appreciate if any guidance or clues of this matter.

Cheers.

 

[TD2K]

Typically I would expect Process engineering to be developing the answers to these questions. API 650 tanks are typically not designed to withstand much vaccum. Cooling off say 50F would create a vacuum in the tank in the area of 1.5 psi. Why were the breather valves blinded off without some other opening being provided for vacuum protection?

Levels: I would normally expect/allow the level in a tank to go down to minimum say to keep a pump nozzle submerged. Max level would be some distance or capacity (barrels, time) before you totally filled the tank.

Temperature: that depends on your system, how does the product get into this tank, what system does it go through, how hot/cold can it come in at. API 650 tanks are normally limited to 200F unless you use one of the appendices which allows you to go to 500F. Check API 650, I'm not positive about these numbers.

Pressure: That's a function of what the tank has been designed for and the inbreathing/outbreathing requirements and devices to control inbreathing/outbreathing if any.

That's pretty general, not sure if that is what you meant.

 

[IFRs]

The tank's name plate should include the information you are looking for.

 

[MJCronin]

I agree with TD2K...

API-650 tanks are typically designed for a very modest pressure ( ~ 10-15 IWC) and almost no vacuum.

Why were the breather valve nozzles blinded ? What was your reasoning here ? Were the tanks being re-painted ?

http://www.qaqc-construction.com/graphics/Hydro-Test_5.jpg

http://lef.uprm.edu/Failure of two Tanks/Examples vacuum.html

http://webwormcpt.blogspot.com/2008/04/vacuum-hazard-another-catastrophic.html